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Sat, 07 Nov 2026 23:22:53 -0800 (PST) Received: from [192.168.29.246] ([49.37.135.186]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-37265618e11sm3280847eec.7.2026.11.07.23.22.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 07 Nov 2026 23:22:52 -0800 (PST) Message-ID: <875bc537-af18-4d4e-86d0-9bf0ed7992db@oss.qualcomm.com> Date: Sun, 8 Nov 2026 12:52:26 +0530 X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] usb: dwc3: Update nominal max votes for qcom usb To: Konrad Dybcio , Greg Kroah-Hartman , Bjorn Andersson , Konrad Dybcio , Rob Herring , Dmitry Baryshkov , Krzysztof Kozlowski , Conor Dooley Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org References: <20261105100626.2003771-1-akash.kumar@oss.qualcomm.com> Content-Language: en-US From: Akash Kumar In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Proofpoint-Spam-Info: AW1haW4tMjYxMTA4MDAyOSBTYWx0ZWRfX8N42NSa2IbuC Qw92YxpE5+RlsbdqUunGHyvbRfeR0DL388abQFzoUYYM8IbluQ837mNOqRk5xFs1pezFJqJw1cE NimhN9D6Iut+p00ctw3ijYG7vKw+BjY= X-Proofpoint-GUID: UpR2Mu8kb4dwxSP8r9UzgxTyEsTBlKqV X-Authority-Analysis: v=2.4 cv=FrKQbGrq c=1 sm=1 tr=0 ts=6af0234e cx=c_pps a=Uww141gWH0fZj/3QKPojxA==:117 a=TqP+r86b5SBipocsz4eaag==:17 a=IkcTkHD0fZMA:10 a=zJRp6_cAMcgA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=_K5XuSEh1TEqbUxoQ0s3:22 a=n4YLBavcT-XMWCbpQ5sA:9 a=QEXdDO2ut3YA:10 a=PxkB5W3o20Ba91AHUih5:22 X-Proofpoint-ORIG-GUID: UpR2Mu8kb4dwxSP8r9UzgxTyEsTBlKqV X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMTA4MDAyOSBTYWx0ZWRfX1ptJSiWidX5b GWpv61rY5uacv68xXmnW+cG/m17mz6mJZMwXOM7X94rBOURcg1A6jcHkr4Iw1O35pFB/Msj105g 5q0cZ6pZF8zOoGBZktqu4ySy4F92bMvlYHFQCVFp9CWLtZKe9NbC7qq6zy+BA7h0lqogmuKlKC+ YjaQQsnesLSp/jMdIh9acOJmahsNfc/O8fLsbUO0GPIo3dVHiEEd8easPj4H4OxWOJaXHoXEdjY w1NLVBWv4qunOOTRWiezcc7mjcVP5ZbZ3gGEORpQ0z+EXEUKt2+JmFbc64emEeX6ZiQRlNKIiQr a+JIY14jOkNitP6GUaJ5EOJJ5j9zAEuKbSVRMhB1huGh1zPNYSVOoX4riWwiWCM697PJTzWLDFk sZRuXFjT9tYOrzDOD909ysJhQdyJzCVscM+ZUDvZOHDTmSkxq9gksijUq6tQ90b/7ZxAvTil/Lf vzTGL8WlvtRT6GJkWBg== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-11-08_02,2026-11-06_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 clxscore=1015 spamscore=0 priorityscore=1501 impostorscore=0 malwarescore=0 bulkscore=0 lowpriorityscore=0 suspectscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2611040001 definitions=main-2611080029 On 05-11-2026 21:11, Konrad Dybcio wrote: > On 11/5/26 11:02 AM, Akash Kumar wrote: >> Increase the nominal max USB memory bandwidth vote to let DDR scale >> higher within its nominal corner, fixing glitches seen during >> simultaneous USB audio use cases. >> >> USB_MEMORY_PEAK_SS_BW is raised from 2500 MB/s to 4500 MB/s (+2000 >> MB/s, ~1.8x). This ICC vote does not by itself determine DDR > Can we scale this depending of the real speed of the connected > device adjusted for the real data throughput? i.e. if we walk > the tree and min/max as appropriate, we end up with say 10G > wire speed, out of which we can shave off some static overhead > > 4500 MB/s is 36 Gb/s which is way beyond what USB3 can do, in > any configuration. > > Konrad > > Hi Konrad, > > Two things worth separating here: > > 1) The ICC vote is not a USB wire-speed requirement, so it > shouldn't be compared directly against the USB3 line rate. This > number is a DDR/memory-interconnect bandwidth vote; the platform's > interconnect/OPP table is what maps a given vote to a DDR > frequency/voltage corner. 4500 MB/s doesn't mean we expect 36 Gb/s > on the wire - it means we want the memory subsystem's bus matrix to > have enough headroom that the platform's table picks the higher > in-corner DDR frequency instead of pinning it at the lower one. The > vote intentionally carries margin for the aggregate memory traffic > of the whole USB subsystem (descriptors, buffering, concurrent > audio capture/playback, etc.), not just the raw bulk payload of one > device, which is why it doesn't map 1:1 to link speed. > > 2) We do already have a speed-based split for this, just not a > per-device dynamic one. dwc3_qcom_interconnect_init() picks between > the HS and SS vote pairs based on usb_get_maximum_speed() of the > controller: > > max_speed = usb_get_maximum_speed(qcom->dwc.dev); > if (max_speed >= USB_SPEED_SUPER || max_speed == USB_SPEED_UNKNOWN) > ret = icc_set_bw(qcom->icc_path_ddr, > USB_MEMORY_AVG_SS_BW, USB_MEMORY_PEAK_SS_BW); > else > ret = icc_set_bw(qcom->icc_path_ddr, > USB_MEMORY_AVG_HS_BW, USB_MEMORY_PEAK_HS_BW); > > This patch only touches the SS tier's peak value; a controller > whose maximum speed is HS is unaffected. It's set once at probe > based on the controller's maximum capability rather than walking > the topology for the actually-negotiated speed of whatever is > plugged in at a given moment, so it's intentionally a worst-case > value rather than a precise per-device figure - which is also why > it's sized for the glitch we saw under concurrent audio+bulk load > rather than for a single device's best-case throughput. > > Thanks, > Akash